Eight individuals, among them two Boeing staff members, lost their lives when a US Air Force B-52 bomber crashed shortly after departing from Edwards Air Force Base in Southern California.
The event took place at 11:20 local time (19:20 GMT) on Monday as the aircraft was engaged in a standard test mission. The crash generated a massive column of black smoke visible for miles.
"Today, Edwards Air Force Base endured a devastating tragedy, and we lost eight outstanding Americans," stated Col James Hayes, characterizing them as a "mixed group of military personnel, government civilians, and government contractors."
Earlier, the base reported that preliminary assessments suggest the crash "was not survivable."
The crew's relatives are being informed, and their identities will be disclosed 24 hours afterward, Hayes said during an afternoon press briefing.
The crash was "fully confined" to the runway within Edwards Air Force Base, Hayes noted, and the base has temporarily halted operations.
The B-52 was involved in the base's radar modernization initiative, he explained, and it crashed right after takeoff, erupting into flames.
After examining initial video footage, the event was deemed "an unrecoverable crash and unsurvivable," Hayes stated.
No cause has been identified yet, and it will not be until after a series of probes, which may take up to 30 days. Additional cause analysis investigations could extend beyond six months, Hayes added.
In a separate announcement, Boeing verified that two of its workers were among those on board and that the company is in touch with their families. The aerospace company declined to provide further comments when reached by the BBC.
In a post on X, California Governor Gavin Newsom described the crash as "a tragic incident" and extended sympathies to the victims' families and the Edwards Air Force Base community.
The Boeing B-52 Stratofortress has been in service with the US military since the 1950s. It is known by the nickname "the Buff," partly an abbreviation for "Big Ugly Fat."
Aerial footage revealed a charred, smoking area where the crash occurred.
In an earlier update on X, the base stated that "the airfield has been closed, and all inbound aircraft are being redirected."
"All non-commercial visitor passes have been suspended until further notice to allow the installation to concentrate entirely on emergency response operations."
The B-52 is a long-range strategic bomber that has taken part in bombing missions during the US and Israel's conflict in Iran.
Capable of flying at altitudes up to 50,000 feet—compared to commercial airliners, which typically cruise at around 35,000 feet—the massive bomber's 70,000lb (32,000kg) payload can include hundreds of conventional bombs and 32 nuclear cruise missiles.
The aircraft can refuel mid-flight, giving it a potentially unlimited strike range. This provided a "nuclear umbrella" for the United States during the Cold War, in the era of mutually assured destruction in the mid-20th Century.
These planes usually carry a crew of five—an aircraft commander, pilot, radar navigator, navigator, and electronic warfare officer.
Edwards Base is situated approximately 100 miles (160km) north of Los Angeles, in the Mojave Desert.
"Absolutely heartbreaking. God bless the 8 crew members on board," US Representative Vince Fong, whose California congressional district includes part of the base, wrote on X.
Congressman Jay Obernolte, whose district also covers part of the base, posted on Facebook that he and his wife "are praying for everyone involved in today's B-52 crash at Edwards Air Force Base, especially the crew, their families, and the first responders on scene."
Michigan Congresswoman Lisa McClain also commented on the crash, posting on X: "My prayers are with everyone involved in the B-52 crash at Edwards Air Force Base this afternoon."
She thanked emergency crews and added: "Our service members carry the weight of this nation's defense every single day. We are with them."